Method and apparatus for micro-treating iron-based alloy, and the material resulting therefrom

Abstract

The invention discloses a process and apparatus for micro-treating an iron-based alloy including heating and immediately quenching to room temperature to produce high tensile iron-based alloy with varying thicknesses. The process may or may not be practiced with or without tension under various controllable tensions in order to create desirable effects The micro-treated iron-based alloy contains desirable bainite to increase its formability and tensile strength. The varying thickness of the iron-based alloys is desirable for different applications, such as forming automobile panels.

What is claimed is: 
     
       1. A method for micro-treating steel, said method comprising:
 providing steel having a first micro-structure and a first thickness, said steel being capable of transforming to steel having a second micro-structure and a second thickness upon being rapidly heated to a selected temperature and then being immediately quenched; 
 feeding continuously the steel along a path of motion to a first tensioning unit at a feed rate; 
 rapidly heating, within 5 seconds, the steel at a heating unit to a selected temperature above the austenite conversion temperature, said selected temperature being at least 1832 ° F.; 
 wherein the heating is only performed until the selected temperature is reached and then the steel is substantially immediately quenched by quenching unit immediately adjacent the heating unit; 
 drawing the steel by a second tensioning unit at a draw rate of no more than 50 % higher than the feed rate to form a section of the steel having a second micro-structure and a second thickness. 
 
     
     
       2. The method of  claim 1 , wherein the steel contains carbon in a range of between 0.001 percent carbon by weight (wt %) to 4 percent carbon by weight (wt %). 
     
     
       3. The method of  claim 1 , wherein the first thickness is about 0.009 to about 0.250 inch. 
     
     
       4. The method of  claim 3 , wherein the first thickness is about 0.065 inch. 
     
     
       5. The method of  claim 1 , further including a pre-heating step to heat the steel to a temperature below the austenitic conversion temperature. 
     
     
       6. The method of  claim 1 , wherein the first and second tensioning units are selected from the group consisting of a pair of hydraulic pressure drawing rollers, drive capstans, and elongation drives. 
     
     
       7. The method of  claim 1 , wherein the feed rate is about 7 to 12 ipm. 
     
     
       8. The method of  claim 7 , wherein the feed rate is 0.75 ipm. 
     
     
       9. The method of  claim 1 , wherein the heating unit is selected from the group consisting of electric resistance, fluidized beds, electric furnaces, plasma furnaces, microwave ovens, open environment propane forges, gas fired unit, solid fuels, high temperature salt baths, induction heaters and torches. 
     
     
       10. The method of  claim 1 , wherein the heating unit transfers heat by a way selected from the group consisting of radiation, electrical resistance, conduction, convection, and induction. 
     
     
       11. The method of  claim 1 , wherein the heating unit includes propane torches. 
     
     
       12. The method of  claim 1 , wherein the selected temperature is at least approximately 1900 ° F. 
     
     
       13. The method of  claim 1 , wherein the selected temperature is between 1900 and 2350 ° F. 
     
     
       14. The method of  claim 1 , wherein the quenching unit adapts a quenching means selected from the group consisting of water, water-containing aqueous solutions, oil, molten salt, brine solutions, air, and powders. 
     
     
       15. The method of  claim 1 , wherein the draw rate is about 12 to 17 ipm. 
     
     
       16. The method of  claim 1 , wherein the second thickness is about 0.030 to 0.080 inch. 
     
     
       17. A method for micro-treating a strip of steel, said method comprising:
 providing a strip of steel having a first micro-structure, a first thickness and a first width, the steel being capable of transforming to a steel having a second micro-structure, a second thickness and a second width upon being rapidly heated to a selected temperature and then being immediately quenched; 
 feeding continuously the strip steel along a path of motion to a first tensioning unit at a feed rate; 
 rapidly heating, within 5 seconds, the strip steel under tension at a heating unit to a selected temperature above the austenite conversion temperature, said selected temperature being at least 1832 ° F.; 
 wherein the heating is only performed until the selected temperature is reached and then the strip steel is substantially immediately quenched by a quenching unit immediately adjacent the heating unit; 
 drawing the strip steel by a second tensioning unit at a draw rate of no more than 50% higher than the feed rate to form a section of the strip steel having a second micro-structure, a second thickness and a second width. 
 
     
     
       18. The method of  claim 17 , wherein the strip of steel contains carbon in a range of between 0.001 percent carbon by weight (wt %) to 4 percent carbon by weight (wt %). 
     
     
       19. The method of  claim 17 , wherein the first thickness is about 0.009 to 0.250 inch. 
     
     
       20. The method of  claim 19 , wherein the first thickness is about 0.065 inch. 
     
     
       21. The method of  claim 17 , further including a pre-heating step to heat the strip steel to a temperature below the austenitic conversion temperature. 
     
     
       22. The method of  claim 17 , wherein the first width is about 2 to 5 inches. 
     
     
       23. The method of  claim 17 , wherein the first width is about 3 inches. 
     
     
       24. The method of  claim 17 , wherein the first and second tensioning units are selected from the group consisting of a pair of hydraulic pressure drawing rollers, drive capstans, and elongation drives. 
     
     
       25. The method of  claim 17 , wherein the feed rate is about 7 to 12 ipm. 
     
     
       26. The method of  claim 25 , wherein the feed rate is 10.75 ipm. 
     
     
       27. The method of  claim 17 , wherein the heating unit is selected from the group consisting of electric resistance, fluidized beds, electric furnaces, plasma furnaces, microwave ovens, induction heaters, open environment propane forges, gas fired unit, solid fuels, high temperature salt baths and torches. 
     
     
       28. The method of  claim 17 , wherein the heating unit transfers heat by a way selected from the group consisting of radiation, electrical resistance, conduction, convection, and induction. 
     
     
       29. The method of  claim 17 , wherein the heating unit includes propane torches. 
     
     
       30. The method of  claim 17  wherein the selected temperature is at least approximately 1900 ° F. 
     
     
       31. The method of  claim 30 , wherein the selected temperature is between 1900 and 2350 ° F. 
     
     
       32. The method of  claim 17 , wherein the quenching unit adapts a cooling means selected from the group consisting of water, water-containing aqueous solutions, oil, molten salt, brine solutions, air, and powders. 
     
     
       33. The method of  claim 17 , wherein the draw rate is about 12 to 17 ipm.